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Conventional wisdom tells us to eat less and exercise more to remain healthy. So far, modern science has corroborated this view. But now there is a twist in the tale. Scientists, indeed, agree that both reducing calorie intake and exercise are necessary if you want live in good health into ripe old age. But if you have to choose between the two, what would you do? Our common sense might tell us to choose exercise, but recent research indicates that calorie restriction is more valuable.
Physiologists had suspected this fact for some time. Limited experiments in humans had shown that the restriction of calorie intake is more beneficial than exercise. They did not know why, although they had a few hypotheses. Now scientist Derek Hoffman and his colleagues at the Albert Einstein College of Medicine in New York have confirmed this finding, and provided evidence to indicate that calorie restriction produces hormonal changes that are beneficial for improved health and longevity.
The findings come close on the heels of other studies that provide evidence for many more benefits of calorie restriction. For example, University of Texas researchers found last month that calorie restriction in rats reduces pre-cancerous lesions in the pancreas. A few months ago, another study by scientists at the Washington University School of Medicine found that year-long calorie restriction improved cardiac function considerably, although exercise had similar effects too. Most of these studies are on rats, but they all give the same message: lose weight and remain lean by eating less and not by exercising more.
It is not as if exercise has no benefit. In fact, exercise is known to be good for improving cardiac health, and more human beings die of cardiac problems than rats do. Exercise confers many other health benefits too. It increases endorphin production (which makes us feel good) and improves hormone levels and brain function. It also protects against many neurological diseases. Yet there are aspects of exercise that are still not well understood. Says Huffman, “From a human perspective, the long-term effects of calorie restriction and exercise are unknown. Therefore, the optimal health prescription should still include a diet that emphasises portion control and a consistent regimen of exercise or physical activity.”
Scientists have found that the rats that exercised regularly lived longer than those that did not. This obviously shows that exercise provides health benefits for animals. But this finding is tempered by a few other findings. In two groups of rats, one that exercised and one that did not, the rats that lived the longest lived till the same age. So they found that while exercise can prevent early death (which is why it increased the average lifespan of the group) it does not increase the lifespan of all individual rats. Again, when they compared one group that exercised with one that ate less but did not exercise, the rats that lived the longest were in the group that ate less.
There have been many theories to explain these surprising results. One theory is that exercising damages DNA and tissues. However, there is scanty evidence to support this. Another theory is that calorie restriction produces positive changes in the body. Hoffman and his colleagues had designed experiments to test these theories and come up with alternatives if they were found wanting. Their results may have significant implications for human beings, although scientists say that we should exercise caution in interpreting them.
One of the first findings is that mice that ate more had higher insulin levels in their blood, regardless of whether they exercised or not. High level of insulin is a risk factor for Type II diabetes in rats as well as humans. Rats that ate a lot but did not exercise had high levels of a type of molecule called Insulin-like Growth Factor (IGF-1). This molecule plays an important role in cell growth and death. In the group that exercised more, there was a higher level of a protein called heat shock protein. This indicated some tissue damage from exercise, but there was no change in other indicators of tissue damage.
Most significantly, in the groups that exercised and had a lower calorie intake, the scientists found lower levels of molecules that indicated DNA damage. The highest levels were in those that ate a lot and did not exercise. And the group that had a low calorie intake had low levels of these molecules. This indicated that DNA damage, which increases normally with age, can be reduced by both low calorie intake and exercise.
So what do these results mean for human beings? As mentioned, a limited number of studies on human beings show the same results. Calorie restriction is a difficult experiment to conduct in human beings. Hungry rats cannot complain, but human beings do, and it is difficult to deprive them of food. Says Huffman: In rodent studies, calorie restriction is easy to define, since we always have a control group that eats all they want, thus we can reduce the food intake in our restricted group by a percentage of control. In humans, it is more difficult to establish a control group. Yet the evidence in favour of calorie restriction is impressive, and still mounting.
You may click to see :-The Quest to learn Why Slashing Calories Extends Life
Sources: The Telegraph (Kolkata, India)